day 18

day18/part1.lua

@@ -0,0 +1,141 @@
+#!/usr/bin/env luajit
+require("utils")
+
+function parse(line)
+	local number = {}
+	local depth = 0
+	for char in chars(line) do
+		if char == "[" then
+			depth = depth + 1
+		elseif char == "]" then
+			depth = depth - 1
+		elseif char ~= "," then
+			table.insert(number, { d=depth, n=tonumber(char) })
+		end
+	end
+	return number
+end
+
+function add(a, b)
+	local sum = {}
+	for i, digit in ipairs(a) do
+		table.insert(sum, { d = digit.d + 1, n = digit.n })
+	end
+	for i, digit in ipairs(b) do
+		table.insert(sum, { d = digit.d + 1, n = digit.n })
+	end
+	return sum
+end
+
+function explode(a)
+	local new = {}
+	local exploded = false
+	local i = 1
+	while i <= #a do
+		if exploded or a[i].d <= 4 then
+			table.insert(new, a[i])
+			i = i + 1
+		else
+			exploded = true
+			if #new > 0 then
+				new[#new].n = new[#new].n + a[i].n
+			end
+			table.insert(new, { d = a[i].d - 1, n = 0 })
+			if #a >= i + 2 then
+				table.insert(new, { d = a[i + 2].d, n = a[i + 1].n + a[i + 2].n })
+			end
+			i = i + 3
+		end
+	end
+	return exploded, new
+end
+
+-- printtable({ explode(parse("[[[[[9,8],1],2],3],4]")) })
+-- printtable({ explode(parse("[7,[6,[5,[4,[3,2]]]]]")) })
+-- printtable({ explode(parse("[[6,[5,[4,[3,2]]]],1]")) })
+-- printtable({ explode(parse("[[3,[2,[1,[7,3]]]],[6,[5,[4,[3,2]]]]]")) })
+-- printtable({ explode(parse("[[3,[2,[8,0]]],[9,[5,[4,[3,2]]]]]")) })
+
+function split(a)
+	local new = {}
+	local split = false
+	for i, digit in ipairs(a) do
+		if split or digit.n < 10 then
+			table.insert(new, digit)
+		else
+			split = true
+			table.insert(new, { d = digit.d + 1, n = math.floor(digit.n / 2) })
+			table.insert(new, { d = digit.d + 1, n = math.ceil(digit.n / 2) })
+		end
+	end
+	return split, new
+end
+
+function reduce(a)
+	local changed = true
+	repeat
+		changed, a = explode(a)
+		if not changed then
+			changed, a = split(a)
+		end
+	until not changed
+	return a
+end
+
+function reconstruct(number)
+	local function go(d, c)
+		local left, right
+		if number[c].d > d then
+			left, c = go(d + 1, c)
+			right, c = go(d + 1, c)
+			return { left, right }, c
+		else
+			return number[c].n, c + 1
+		end
+	end
+	return go(0, 1)
+end
+
+function printnumber(a)
+	local function go(a)
+		if type(a) == "number" then
+			io.write(tostring(a))
+		else
+			io.write("[")
+			go(a[1])
+			io.write(",")
+			go(a[2])
+			io.write("]")
+		end
+	end
+	go(reconstruct(a))
+	io.write("\n")
+end
+
+-- printnumber(reduce(parse("[[[[[4,3],4],4],[7,[[8,4],9]]],[1,1]]")))
+-- printnumber(reduce(add(parse("[[[[4,3],4],4],[7,[[8,4],9]]]"),parse("[1,1]"))))
+-- printnumber(parse("[[[0,[4,5]],[0,0]],[[[4,5],[2,6]],[9,5]]]"))
+-- printtable(parse("[[[0,[4,5]],[0,0]],[[[4,5],[2,6]],[9,5]]]"))
+-- printnumber(add(parse("[[[0,[4,5]],[0,0]],[[[4,5],[2,6]],[9,5]]]"),parse("[7,[[[3,7],[4,3]],[[6,3],[8,8]]]]")))
+-- printnumber(reduce(add(parse("[[[0,[4,5]],[0,0]],[[[4,5],[2,6]],[9,5]]]"),parse("[7,[[[3,7],[4,3]],[[6,3],[8,8]]]]"))))
+
+function magnitude(a)
+	local function go(a)
+		if type(a) == "number" then
+			return a
+		else
+			return 3 * go(a[1]) + 2 * go(a[2])
+		end
+	end
+	return go(reconstruct(a))
+end
+
+local f = io.open(arg[3])
+local number = parse(f:read("*l"))
+local line = f:read("*l")
+while line do
+	number = reduce(add(number, parse(line)))
+	line = f:read("*l")
+end
+
+print(magnitude(number))

day18/part2.lua

@@ -0,0 +1,135 @@
+#!/usr/bin/env luajit
+require("utils")
+
+function parse(line)
+	local number = {}
+	local depth = 0
+	for char in chars(line) do
+		if char == "[" then
+			depth = depth + 1
+		elseif char == "]" then
+			depth = depth - 1
+		elseif char ~= "," then
+			table.insert(number, { d=depth, n=tonumber(char) })
+		end
+	end
+	return number
+end
+
+function explode(a)
+	local new = {}
+	local exploded = false
+	local i = 1
+	while i <= #a do
+		if exploded or a[i].d <= 4 then
+			table.insert(new, a[i])
+			i = i + 1
+		else
+			exploded = true
+			if #new > 0 then
+				new[#new].n = new[#new].n + a[i].n
+			end
+			table.insert(new, { d = a[i].d - 1, n = 0 })
+			if #a >= i + 2 then
+				table.insert(new, { d = a[i + 2].d, n = a[i + 1].n + a[i + 2].n })
+			end
+			i = i + 3
+		end
+	end
+	return exploded, new
+end
+
+function split(a)
+	local new = {}
+	local split = false
+	for i, digit in ipairs(a) do
+		if split or digit.n < 10 then
+			table.insert(new, digit)
+		else
+			split = true
+			table.insert(new, { d = digit.d + 1, n = math.floor(digit.n / 2) })
+			table.insert(new, { d = digit.d + 1, n = math.ceil(digit.n / 2) })
+		end
+	end
+	return split, new
+end
+
+function reduce(a)
+	local changed = true
+	repeat
+		changed, a = explode(a)
+		if not changed then
+			changed, a = split(a)
+		end
+	until not changed
+	return a
+end
+
+function add(a, b)
+	local sum = {}
+	for i, digit in ipairs(a) do
+		table.insert(sum, { d = digit.d + 1, n = digit.n })
+	end
+	for i, digit in ipairs(b) do
+		table.insert(sum, { d = digit.d + 1, n = digit.n })
+	end
+	return reduce(sum)
+end
+
+function reconstruct(number)
+	local function go(d, c)
+		local left, right
+		if number[c].d > d then
+			left, c = go(d + 1, c)
+			right, c = go(d + 1, c)
+			return { left, right }, c
+		else
+			return number[c].n, c + 1
+		end
+	end
+	return go(0, 1)
+end
+
+function printnumber(a)
+	local function go(a)
+		if type(a) == "number" then
+			io.write(tostring(a))
+		else
+			io.write("[")
+			go(a[1])
+			io.write(",")
+			go(a[2])
+			io.write("]")
+		end
+	end
+	go(reconstruct(a))
+	io.write("\n")
+end
+
+function magnitude(a)
+	local function go(a)
+		if type(a) == "number" then
+			return a
+		else
+			return 3 * go(a[1]) + 2 * go(a[2])
+		end
+	end
+	return go(reconstruct(a))
+end
+
+local numbers = {}
+for line in io.lines(arg[3]) do
+	table.insert(numbers, parse(line))
+end
+
+local max = 0
+for i, a in pairs(numbers) do
+	for j, b in pairs(numbers) do
+		if i ~= j then
+			local m = magnitude(add(a, b))
+			if m > max then max = m end
+		end
+	end
+end
+
+print(max)

utils.lua

@@ -32,7 +32,7 @@ function printtable(t, nonewline)
 			printtable(v, true)
 			io.write(") ")
 		else
-			io.write(v.." ")
+			io.write(tostring(v).." ")
 		end
 	end
 	if not nonewline then